Heel unit of a ski safety binding



FIG. 1 is a side elevational view of a heel unit of a ski safety binding showing my new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a bottom plan view thereof; and

FIG. 5 is a top plan view thereof. 

The ornamental design for a heel unit of a ski safety binding, as shown. 